A process for the manufacturing of composite metal wire

ABSTRACT

The process for manufacturing a composite metal wire comprises extruding and coating a metal onto a metallic core wire. By this method, a traction force is added to the produced composite wire and said core wire is heated, making possible the production of a composite metal wire provided with a metal layer which can be extruded at lower temperature than the core wire and increasing the corrosion resistance of the core wire.

United States Patent [is] 3,646,796

Tanaka et al. 1 Mar. 7, 1972 [54] A PROCESS FOR THE [56] am Clted MANUFACTURING 0F COMPOSITE UNITED STATES PATENTS METAL WIRE Inventors: Eihachiro Tamika, Sendai-shi; Takeli Fukuda, Kanuma-shi; Kenkichl Yamail; Yasuhiko Miyake; Hiroshi Ota; Katsuo Kimura, l-litachi-shi, all of Japan Hitachi Cable Limited, Chiyoda-ku, Tokyo, Japan Filed: Sept. 26, 1969 Appl. No.: 861,392

Assignee:

Foreign Application Priority Data Sept. 28, 1968 Japan ..43/70353 U.S. Cl. ..72/258, 72/268 Int. Cl ..B2lc 23/22, B2le 25/02 Field of Search ..72/258, 268

Pn'mary Examiner-Richard J. Herbst Assistant Examiner-R. M. Rogers AttorneySughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT lClaims,4DrawingFigures A PROCESS FOR THE'MANUFACTURING OF COMPOSITE METAL WIRE BACKGROUND OF THE INVENTION This invention relates to a process for making a composite wire having a coating of an electrically conductive material, such as aluminum or an aluminum alloy, on a core wire, such as an iron or steel wire.

More particularly, the present invention provides a process for making a composite wire having a coating of a metal which is softer and possesses less electrical resistance, compared with steel, and which increases the corrosion resistance of steel, such as aluminum, aluminum alloy, copper, copper alloy, lead, tin, or cadmium, on a steel wire. Other embodiments capable of production by the present process are composite wires having a coating of a metal which can be extruded at a lower temperature than the core wire and which increases the corrosion resistance of the core wire, such as zinc, lead, or cadmium on a core wire of copper, aluminum, or their alloys.

Many attempts to coat a metal differing from the metal of the core wire and having a lower extruding temperature than that of the core wire onto a metal core wire have also been made by applicants.

The apparatus employed for the extrusions in such attempts is shown in FIG. 1 as a simplified view. Numeral l in the drawing is a container, 2 is a mandrel, 3 is a die for extrusion, 4 is a stem, is the core wire, is a metal billet to be coated on the core wire, and 16 is the metallic layer coated by extrusion.

The main disadvantages occurring in such attempts were as follows:

I. The extrusion rate became extremely low or extrusion was stopped entirely when the thickness of said coated metallic layer was lowered below a certain value.

2. Even if the thickness of the coated layer was above said certain value, the extrusion became impossible or the extrusion rate became extremely low when the aperture between the mandrel 2 and the die 3 was above a certain value.

3. When said aperture was less than another certain value, the bonding or adherence between the core wire 10 and the metallic coating layer 16 became inferior, and accordingly, various limitations on the practical coating operation occurred.

4. In view of the reasons mentioned above in l and 2, the

size range of industrial products coated by this method has been restricted and thus the method has proved to be uneconomical.

SUMMARY OF THE INVENTION An object of the present invention is, therefore, to provide a method for manufacturingsaid composite wire economically, overcoming the above problems.

Another object of this invention is to provide a novel method for manufacturing said composite wire effectively with a decreased cost.

A method of manufacturing a composite wire by extruding and coating a different metal onto the metal of the core wire, comprising adding the tractive force which is below the tensile rupture strength of the composite metal wire itself to the extruded composite wire, heating the circumference of said core wire during or before the coating of said different extruding metal and further heating said metal just before extrusion by the thermal energy of said heated core wire to decrease the plastic flow resistance of the metal and to increase the extrusion and coating rate.

Briefly described, in other words, the manufacturing method in accordance with the present invention comprises means to provide the tractive force to the product formed by extrusion and means to heat the metal to be formed into the core wire.

DETAILED DESCRIPTION OF THE INVENTION As the means to provide the aforesaid tractive force, a tension lower than the rupture strength of the core wire 10 and 1, is applied to said core wire 10 and said metal layer 16 in a forward direction, as shown by the arrow. Thus, the deformation of metallic billet 15 to be extruded through die 3 is accelerated remarkably and the thickness of the extrudable metallic layer 16 and the extrusion rate is increased.

Said heating means for the core wire may not be particularly restricted, so long as it takes place before the immersion of the core wire 10 together with the metallic billet 15 to beextruded from the die 3. For instance, the core'wire I0 may either be heated in the billet 15 or may be drawn in after being heated in the mandrel 2. As the heating source, any of an electric resistance furnace, a combustion furnace employing a gaseous or liquid fuel, a highor low-frequency induction heater, or direct electric heating means may be employed, as desired.

The heating temperature is suitably selected according-to the material of the core wire to be used, the material of the metallic layer to be coated thereon, and the extrusion rate. In general, a rising temperature has a tendency to increase the extrusion rate and to decrease the tensile strength and hardness of the core wire. In practical processing, about 300 to 600 C. is most preferable.

There are many advantages to be obtained by heating the core wire during the extrusion and coating. Usually, the metallic material to be extruded onto the core wire is heated to a certain temperature and when the core wire, whose temperature is lower than said temperature, is drawn in, the deformation resistance increases and the extrusion rate is lowered. Such cooling can be prevented by drawing in a heated core wire in accordance with'the present invention. From this viewpoint, it is preferred to heat the metallic billet tobe coated to the same temperature as the core wire, although it is recognized that heating said core wire to either a somewhat lower or higher temperature may also be effective and advantageous.

The industrial advantages that can be accomplished by the method of the present invention are in the expanding of the kinds of materials which may be extruded, enlarging the temperature range for extrusion and a remarkable increase in the extrusion rate. The technical advantages are to be found in the considerable decrease in the force needed for extrusion and coating and the pressing force of the stem 4 by addition of the forward tension.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described by referring to the accompanying figures, wherein the addition of traction force by forward tension and heating the core wire will be described, respectively, for a clearer understanding of the present invention.

FIG. 1 is a diagrammatic assembly view of the extruding apparatus employed in the extrusion method of the present invention.

FIG. 2 is a general view of direct current heating of the core wire.

FIG. 3 is a curve showing the relationship between the temperature of the steel core wire and the extrusion rate.

FIG. 4 is a curve showing the relationship between the electric voltage and the extrusion rate.

A steel wire of 2.3 mm. in diameter as the core wire 10 and a pure aluminum billet 15 were prepared. Said billet was extruded by use of the extruding apparatus as shown in FIG. I through the die 3 having an aperture of 2.6 mm. in diameter after being heated to 500 C. I

The relationship between the increase of forward tension- Example Extruding Rate Forward Tension No. in kg. in m'./min.

3 I50 0.4] 4 200 0.86 5 250 L4 6 300 L9 7 350 2.3 8 450 2.9 9 550 3.8

In the above examples, the products exhibited an undesirable tendency to uneveness, a decrease in the thickness of the extruded coating and, in some cases, a rupturing of said coatings.

Next, employing the same conditions as above, but increasing the temperature of the steel wire and the extruding temperature by heating the core wire 10, the results shown in FIG. 3 were obtained. The heating means used herein was the direct current heating apparatus shown in FIG. 2, in which apparatus the voltage was added between the electrode rolls 6 and 6' and the brush 7 and 7 provided thereon. Said rolls 6 and 6' were provided about 2 m. apart and were placed at a distance of 1.5 m. behind the die 3 in FIG. 1.

FIG. 4 shows the increasing rate of the extruding velocity related to increasing the current voltage.

The curve 31 in FIG. 3 indicates the lower limit of temperature that is preferable upon heating the steel wire. The curve 32 indicates the preferable upper limit of temperature. Similarly, curve 41 in FIG. 4 indicates the lower limit of voltage for introducing current into the steel wire and curve 42 the preferable upper limit. Of course, these limits are only for the case of using the particular extruding apparatus, material and heating means described above, and are not intended to indicate a general limitation on the practice of the present invention. It is to be clearly understood from FIG. 3 and FIG. 4 that the extruding rate is remarkably increased by raising the heating temperature of the steel core wire 10. In both drawings, the zone shown by legends A and B indicates the range wherein extrusion is possible and the zone shown by the legend C indicatesthe range wherein extrusion is impossible. Zone A is the most preferable extrusion range. Zone 8 extrusions tend to possess comparatively incomplete bonding and undesirable mechanical properties. Zone C is a range wherein it is almost impossible to extrude a metal onto the surface of the core wire.

From FIG. 3, it can be recognized that a suitable temperature for the steel wire in industrial extruding and coating of aluminum onto steel wire is in the range of 300 to 600 C.

The extruding apparatus and the heating means employed in the process of the present invention are not limited to those illustrated in FIGS. 1 and 2 and may be changed into various forms, constructions and arrangements as desired. The

method of this invention is equally applicable to the use of copper or aluminum as the core wire 10 and to the coating of zinc, magnesium, lead, tin, or cadmium as the billet 15.

There are many advantages to the composite metal wire produced according to the present invention.

The composite wire obtained by using a steel wire as the core wire coated with copper or aluminum can be used as an electric supply wire. In this case, the copper or aluminum coated thereon has the effect of protecting the steel or iron wire, ordinarily easily rusted, from corrosion.

We claim:

1. A process for the production of a composite metal wire provided with a metallic layer on a metallic core wire comprising directing a metallic core wire through the die of an extrusion apparatus, providing a forward traction force of 250-550 kg. to said core wire, heating said core wire to approximately 600 C. prior to passing the wire through said extrusion apparatus, heating the metal billet to be extruded to approximately 500 C. and extruding a metallic layer on said heated metallic core wire as said wire is pulled through said die whereby the thermal energy of said heated core wire decreases the plastic flow resistance. of the metal to be extruded thereby increasing the extrusion coating rate. 

